The long range goal of the proposed research project is to obtain an understanding of the mechanism of regulation in eukaryotic cells and to relate such information to the metabolism of cancer cells. The yeast Saccharomyces will be used as a model system. Cancer cells are characterized by an altered growth rate and morphology (both of which can be reversed by cyclic AMP in certain cultured tissues) and an altered respiration. Therefore, more specifically, glucose repression and its role in the regulation of enzyme synthesis and mitochondrial biogenesis will be studied by isolating mutations involving these aspects of yeast metabolism. In yeast, the biogenesis of mitochondria and the synthesis of the maltose, galactose and melibiose fermentation enzymes is repressed by glucose. Methods are described by which one can isolate mutants of the glucose repression system. The mutants will be characterized genetically to determine the mode of inheritance (cytoplasmic or nuclear, number of loci, etc.), and biochemically by enzyme determinations for a number of glucose sensitive loci and cyclic AMP levels. (This should indicate whether cyclic AMP is of central importance for glucose repression in yeast, as it is in bacteria.) The effect of glucose on the transcription of glucose repression sensitive loci in varying states of repression and derepression in both wild-type and mutant strains will be determined. These studies will be done by DNA-RNA hybridization in which the DNA probe will be a recombinant plasmid carrying the glucose sensitive yeast gene.